title: Solvent annealing induced phase separation and dewetting in PMMA∕SAN blend film: film thickness and solvent dependence.
abstract: The competition between "dewetting" and "phase separation" behaviors in polymer blend films attracts significant attention in the last decade. The simultaneous phase separation and dewetting in PMMA∕SAN [poly(methyl methacrylate) and poly(styrene-ran-acrylonitrile)] blend ultrathin films upon solvent annealing have been observed for the first time in our previous work. In this work, film thickness and annealing solvent dependence of phase behaviors in this system has been investigated using atomic force microscopy and grazing incidence small-angle X-ray scattering (GISAXS). On one hand, both vertical phase separation and dewetting take place upon selective solvent vapor annealing, leading to the formation of droplet∕mimic-film structures with various sizes (depending on original film thickness). On the other hand, the whole blend film dewets the substrate and produces dispersed droplets on the silicon oxide upon common solvent annealing. GISAXS results demonstrate the phase separation in the big dewetted droplets resulted from the thicker film (39.8 nm). In contrast, no period structure is detected in small droplets from the thinner film (5.1 nm and 9.7 nm). This investigation indicates that dewetting and phase separation in PMMA∕SAN blend film upon solvent annealing depend crucially on the film thickness and the atmosphere during annealing.
authors.affiliation: College of Material, Chemistry and Chemical Engineering, Hangzhou Normal University, No. 16 Xuelin Rd., Xiasha High-tech Zone, Hangzhou 310036, People's Republic of China. youjichun@126.com
authors.forename: Jichun
authors.initials: J
authors.lastname: You
authors.forename: Shuangshuang
authors.initials: S
authors.lastname: Zhang
authors.forename: Gang
authors.initials: G
authors.lastname: Huang
authors.forename: Tongfei
authors.initials: T
authors.lastname: Shi
authors.forename: Yongjin
authors.initials: Y
authors.lastname: Li
mesh_terms: D000181:Acrylonitrile / Q000031:analogs & derivatives* / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D053838:Scattering, Small Angle; D012997:Solvents / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D012997:Solvents; C586117:poly(styrene-ran-acrylonitrile); D019904:Polymethyl Methacrylate; D000181:Acrylonitrile